igneous
Vesicular basalt (probable scoriaceous basalt)
Basalt, composed mainly of plagioclase feldspar, pyroxene, and commonly olivine
AI-generated identification · may be incorrectDark gray to black, fine-grained, dull to weakly glassy, with abundant irregular gas vesicles; hardness about 5–6 Mohs and no prominent cleavage. The pale yellow-green spots may be olivine or weathering products, though the photograph is insufficient for certainty.
Identified More igneous →
Explore Vesicular basalt (probable scoriaceous basalt) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained, dull to weakly glassy, with abundant irregular gas vesicles; hardness about 5–6 Mohs and no prominent cleavage. The pale yellow-green spots may be olivine or weathering products, though the photograph is insufficient for certainty.
Formation & geological history
An extrusive igneous rock formed when mafic lava rapidly cooled at or near the surface, trapping volcanic gases; likely Cenozoic or younger, depending on locality. Its highly porous texture indicates scoria-like cooling near a lava-flow top or volcanic vent.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, and occasionally for decorative specimens. Ordinary pieces have little jewelry value.
Geological facts
Basalt is the most widespread volcanic rock on Earth and forms much of the oceanic crust. Vesicles may later become filled with minerals such as zeolite, calcite, or quartz.
Field identification & locations
Identify it by its black mafic color, low density, rough vesicles, and lack of visible layered sedimentary structure; a streak, density test, and close examination for olivine would help confirm it. Common localities include volcanic regions worldwide, including Hawaii, Iceland, the Deccan Traps, and oceanic islands.
